Proteasomal activator 28 gamma (PA28γ) is frequently overexpressed in hepatocellular carcinoma; however, its underlying mechanism and role in hepatitis B virus (HBV) replication are largely unknown. Here, we found that HBV X protein (HBx) natural variants containing Ser-101 instead of Pro-101 increase reactive oxygen species levels in the mitochondria and activate the ataxia telangiectasia mutated/checkpoint kinase 2 pathway in the nucleus, resulting in the phosphorylation of p53 at Ser-15 and Ser-20 and the subsequent upregulation of its protein levels. Therefore, HBx variants containing Ser-101 induced p53-dependent activation of PA28γ expression in human hepatoma cells. The elevated PA28γ levels upregulated HBx levels through the inhibition of seven in absentia homologue 1-dependent proteasomal degradation. The self-amplifying ability of HBx variants containing Ser-101 via a positive feedback loop involving p53 and PA28γ was accurately reproduced in both a 1.2-mer HBV replicon and in vitro HBV infection systems, which also provided evidence for the stimulation of HBV replication by these HBx variants. In conclusion, the ability of HBx to upregulate PA28γ levels via p53 activation, in a Ser-101-dependent pathway, is critical for the stimulation of HBV replication.
TsugeM,
HiragaN,
AkiyamaR,
TanakaS,
MatsushitaM et al. Hbx protein is indispensable for development of viraemia in human hepatocyte chimeric mice. J Gen Virol2010; 91:1854–1864 [View Article]
XuZ,
YenTSB,
WuL,
MaddenCR,
TanW et al. Enhancement of hepatitis B virus replication by its X protein in transgenic mice. J Virol2002; 76:2579–2584 [View Article]
KeaslerVV,
HodgsonAJ,
MaddenCR,
SlagleBL.
Hepatitis B virus HBx protein localized to the nucleus restores HBx-deficient virus replication in HepG2 cells and in vivo in hydrodynamically-injected mice. Virology2009; 390:122–129 [View Article]
CarmonaS,
ElyA,
CrowtherC,
MoollaN,
SalazarFH et al. Effective inhibition of HBV replication in vivo by anti-HBx short hairpin RNAs. Mol Ther2006; 13:411–421 [View Article]
KeaslerVV,
HodgsonAJ,
MaddenCR,
SlagleBL.
Enhancement of hepatitis B virus replication by the regulatory X protein in vitro and in vivo. J Virol2007; 81:2656–2662 [View Article]
HenklerF,
HoareJ,
WaseemN,
GoldinRD,
McGarveyMJ et al. Intracellular localization of the hepatitis B virus HBx protein. J Gen Virol2001; 82:871–882 [View Article]
ChaMY,
RyuDK,
JungHS,
ChangHE,
RyuWS.
Stimulation of hepatitis B virus genome replication by HBx is linked to both nuclear and cytoplasmic HBx expression. J Gen Virol2009; 90:978–986 [View Article]
TangH,
DelgermaaL,
HuangF,
OishiN,
LiuL et al. The transcriptional transactivation function of HBx protein is important for its augmentation role in hepatitis B virus replication. J Virol2005; 79:5548–5556 [View Article]
RawatS,
BouchardMJ.
The hepatitis B virus (HBV) HBx protein activates Akt to simultaneously regulate HBV replication and hepatocyte survival. J Virol2015; 89:999–1012 [View Article]
LiX,
AmazitL,
LongW,
LonardDM,
MonacoJJ et al. Ubiquitin- and ATP-independent proteolytic turnover of p21 by the REGgamma-proteasome pathway. Mol Cell2007; 26:831–842 [View Article]
YuG,
ZhaoY,
HeJ,
LonardDM,
MaoCA et al. Comparative analysis of REG{gamma} expression in mouse and human tissues. J Mol Cell Biol2010; 2:192–198 [View Article]
WanZX,
YuanDM,
ZhuoYM,
YiX,
ZhouJ et al. The proteasome activator PA28γ, a negative regulator of p53, is transcriptionally up-regulated by p53. Int J Mol Sci2014; 15:2573–2584 [View Article]
YeomS,
JeongH,
KimSS,
JangKL.
Hepatitis B virus X protein activates proteasomal activator 28 gamma expression via upregulation of p53 levels to stimulate virus replication. J Gen Virol2018; 99:655–666 [View Article]
KimS,
LeeHS,
JiJH,
ChoMY,
YooYS et al. Hepatitis B virus X protein activates the ATM-Chk2 pathway and delays cell cycle progression. J Gen Virol2015; 96:2242–2251 [View Article]
YeomS,
KimSS,
JeongH,
JangKL.
Hepatitis B virus X protein activates E3 ubiquitin ligase Siah-1 to control virus propagation via a negative feedback loop. J Gen Virol2017; 98:1774–1784 [View Article]
WangWH,
GrégoriG,
HullingerRL,
AndrisaniOM.
Sustained activation of p38 mitogen-activated protein kinase and c-Jun N-terminal kinase pathways by hepatitis B virus X protein mediates apoptosis via induction of Fas/FasL and tumor necrosis factor (TNF) receptor 1/TNF-alpha expression. Mol Cell Biol2004; 24:10352–10365 [View Article]
KwunHJ,
JangKL.
Natural variants of hepatitis B virus X protein have differential effects on the expression of cyclin-dependent kinase inhibitor p21 gene. Nucleic Acids Res2004; 32:2202–2213 [View Article]
LeeYI,
HwangJM,
ImJH,
LeeYI,
KimNS et al. Human hepatitis B virus-X protein alters mitochondrial function and physiology in human liver cells. J Biol Chem2004; 279:15460–15471 [View Article]
MatsudaY,
SanpeiA,
WakaiT,
KubotaM,
OsawaM et al. Hepatitis B virus X stimulates redox signaling through activation of ataxia telangiectasia mutated kinase. Int J Clin Exp Pathol2014; 7:2032–2043
FiucciG,
BeaucourtS,
DuflautD,
LespagnolA,
Stumptner-CuveletteP et al. Siah-1b is a direct transcriptional target of p53: identification of the functional p53 responsive element in the siah-1b promoter. Proc Natl Acad Sci USA2004; 101:3510–3515 [View Article]
ZhaoJ,
WangC,
WangJ,
YangX,
DiaoN et al. E3 ubiquitin ligase Siah-1 facilitates poly-ubiquitylation and proteasomal degradation of the hepatitis B viral X protein. FEBS Lett2011; 585:2943–2950 [View Article]
ChaMY,
KimCM,
ParkYM,
RyuWS.
Hepatitis B virus X protein is essential for the activation of Wnt/beta-catenin signaling in hepatoma cells. Hepatology2004; 39:1683–1693 [View Article]
ElmoreLW,
HancockAR,
ChangSF,
WangXW,
ChangS et al. Hepatitis B virus X protein and p53 tumor suppressor interactions in the modulation of apoptosis. Proc Natl Acad Sci USA1997; 94:14707–14712 [View Article]
WangXW,
GibsonMK,
VermeulenW,
YehH,
ForresterK et al. Abrogation of p53-induced apoptosis by the hepatitis B virus X gene. Cancer Res1995; 55:6012–6016
FeitelsonMA,
ZhuM,
DuanLX,
LondonWT.
Hepatitis B X antigen and p53 are associated in vitro and in liver tissues from patients with primary hepatocellular carcinoma. Oncogene1993; 8:1109–1117
WangXW,
ForresterK,
YehH,
FeitelsonMA,
GuJR et al. Hepatitis B virus X protein inhibits p53 sequence-specific DNA binding, transcriptional activity, and association with transcription factor ERCC3. Proc Natl Acad Sci USA1994; 91:2230–2234 [View Article]
AhnJY,
JungEY,
KwunHJ,
LeeCW,
SungYC et al. Dual effects of hepatitis B virus X protein on the regulation of cell-cycle control depending on the status of cellular p53. J Gen Virol2002; 83:2765–2772 [View Article]
JungJK,
KwunHJ,
LeeJO,
AroraP,
JangKL.
Hepatitis B virus X protein differentially affects the ubiquitin-mediated proteasomal degradation of beta-catenin depending on the status of cellular p53. J Gen Virol2007; 88:2144–2154 [View Article]
WangWH,
HullingerRL,
AndrisaniOM.
Hepatitis B virus X protein via the p38MAPK pathway induces E2F1 release and ATR kinase activation mediating p53 apoptosis. J Biol Chem2008; 283:25455–25467 [View Article]
KnollS,
FürstK,
ThomasS,
Villanueva BaselgaS,
StollA et al. Dissection of cell context-dependent interactions between HBx and p53 family members in regulation of apoptosis: a role for HBV-induced HCC. Cell Cycle2011; 10:3554–3565 [View Article]
BlumHE,
ZhangZS,
GalunE,
von WeizsäckerF,
GarnerB et al. Hepatitis B virus X protein is not central to the viral life cycle in vitro. J Virol1992; 66:1223–1227
LeeCW,
SørensenTS,
ShikamaN,
La ThangueNB.
Functional interplay between p53 and E2F through co-activator p300. Oncogene1998; 16:2695–2710 [View Article]
KwakJ,
TiwariI,
JangKL.
Hepatitis C virus core activates proteasomal activator 28γ expression via upregulation of p53 levels to control virus propagation. J Gen Virol2017; 98:56–67 [View Article]
MendyME,
KayeS,
van der SandeM,
Rayco-SolonP,
WaightPA et al. Application of real-time PCR to quantify hepatitis B virus DNA in chronic carriers in the Gambia. Virol J2006; 3:23 [View Article]
SeveriT,
Vander BorghtS,
LibbrechtL,
VanAelstL,
NevensF et al. Hbx or HCV core gene expression in HepG2 human liver cells results in a survival benefit against oxidative stress with possible implications for HCC development. Chem Biol Interact2007; 168:128–134 [View Article]
LimJS,
ParkSH,
JangKL.
Hepatitis C virus core protein overcomes stress-induced premature senescence by down-regulating p16 expression via DNA methylation. Cancer Lett2012; 321:154–161 [View Article]
LeeJO,
KwunHJ,
JungJK,
ChoiKH,
MinDS et al. Hepatitis B virus X protein represses E-cadherin expression via activation of DNA methyltransferase 1. Oncogene2005; 24:6617–6625 [View Article]
PonchelF,
ToomesC,
BransfieldK,
LeongFT,
DouglasSH et al. Real-Time PCR based on SYBR-Green I fluorescence: an alternative to the TaqMan assay for a relative quantification of gene rearrangements, gene amplifications and micro gene deletions. BMC Biotechnol2003; 3:18 [View Article]